Alternating-current system of control.



No. 803,218. PATENTED OCT. 31, 1905.

' F. CONRAD. ALTBRNATING CURRENT SYSTEM OF CONTROL.

APPLICATION FILED APE. 3, 1905.

! WlTNESSES:

lNVENTOR A BY .QW/

A fTORNEY UNITED STATES PATENT OFFICE.

"FRANK CONRAD, OF EDGEVVOOD PARK, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELEC"RIC & MANUFACTURING- COMPANY, A CORPO- RATION OF PENNSYLVANIA.

Specification of Letters Patent.

Patented Oct. 31, 1905.

Application filed April 3, 1905. Serial No. 253,642.

To (all whom it may concern:

Be it known that I, FRANK CONRAD, a citizen of the United States, and aresident of Edgewood Park, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in Alternating-Current Systems of Control, (Case No. 1,417,) of which the following isa specification.

My invention relates to systems of control for electric motors, andparticularly to alternating-current systems that embodyvoltageregulating devices.

The object of my invention is to provide means for causing two or morevoltage-regulators to operate simultaneously and synchronouslythat is,so that all of the regulators will supply approximately the same voltageto the motors or other translating devices.

l/Vhen two or more railway-vehicles that are each provided with motorsand voltageregulators are connected to form a train or when it isexpedient or necessary to provide a single vehicle with twovoltage-regulators, it is desirable that all the motors be supplied withapproximately the same voltage in order that they may operate at thesame speed and develop the same torque.

My invention provides means for causing equalization of the potentialsat the terminals of all of the motors.

The single figure of the accompanying drawing illustrates a systemembodying my invention.

Alternating-current energy is supplied from a trolley-conductor l and atrack-rail 2 to motors 3 and 3 through lowering transformers 4t and 4tand voltage-regulators 5 and 5, that are operated by means of motors 6and 6, the circuits of which are controlled by means ofreversing-switches 7 and 7 and a masterswitch 8. One terminal of themaster-switch 8 is connected to the middle or an intermediate point ofthe secondary winding 9 of a transformer 10, the terminals of theprimary winding 11 of which are connected to correspondingterminals ofthe motors 3 and 3 or r to corresponding points in the motor-circuits.

The terminals of the secondary winding 9 are connectedto'reversing-switches 7 and 7, and the remaining terminal of themaster-switch 8 is connected to intermediate points in the transformers12 and 12, that are supplied directly from the trolley-wire l and thetrackrail 2. The transformers 12 and 12 may in a more complete system ofcontrol than that here shown serve an additional purpose to that hereindicated-such, for instance, as supplying the lights of the train.

The voltage-regulators 5 and 5 comprise primary windings I3 and 13*,that may be adjusted in position with respect to secondary windings 14cand 14 by means of the motors 6 and 6, the inductive relations of theprimary and secondary windings being thereby modified and the voltagesupplied to the motors 3 and 3 varied.

If the regulators 5 are not adjusted synchronously, different voltagesmay be supplied to the motors 3 and 3, and a difference of potential maybe caused to exist between the terminals of the motors, and consequentlybetween the terminals of the primary winding 11 of the transformer 10.The motors 6 and 6 are ordinarily supplied with energy from thetransformers l2 and 12 through the master-switch 8 and through the partsof the secondary winding 9 of the transformer 10 in opposite directions,so that the inductances of the two parts of the windings neutralize eachother. I Vhen, however, current traverses the primary winding 11,electromotive forces are induced in the portions of the secondarywinding 9, one of which is added to the normal voltage derived from thetransformers l2 and 12 and the other of which is opposed to that derivedfrom the transformers 12 and 12".

The circuits are so arranged that whenever the voltages supplied to themain motors differ those supplied to the regulator-operating motors arealso caused to differ and the regulator which is delivering the lowestvoltage is accelerated, while-the other is retarded in its operationuntil the voltages are equalized. For example, it may be supposed thatthe motors 6 and 6 are normally supplied with current at one hundredvolts and that the regulators 5 and 5 do not occupy correspondingpositions and that consequently the voltage supplied to the motor 3 ishigher than that supplied to the motor 3 by ten volts. The difference ofpotential, then, between the terminals of the primary winding 11 of thetransformer 10 is ten volts, and it may be assumed that an electromotiveforce of twenty volts is induced in the secondary winding 9, one-half ofwhich pertains to each part of such winding. In the part 15 the tenvolts will be added to the one hundred volts supplied from the circuit,and consequently the voltage supplied to the motor 6 will be one hundredand ten, while the ten volts induced in the part 16 will be opposed tothe one hundred volts derived directly from the circuit, and thereforethe voltage supplied to the motor 6 will be ninety. The regulator 5 willthen be operated at an increased speed and the regulator 5 at adecreased speed until there is no difference of potential between theterminals of the primary winding 11 of the transformer 10that is, untilthe motors 3 and 3 are supplied With the same voltage.

The arrangement and circuit connections of the main and auxiliarytransformers, of the voltage-regulators, their operating-motors, and themain motors may be varied considerabl y from what is here specificallyshown and described, and the transformers may also be of the two-windingform rather than of the single-Winding form, as here shown, and manyother of the details of the arrangement may be modified withoutdeparting from the scope of my invention.

1 claim as my invention* 1. The combination withaplurality oftranslating devices and voltage-regulators therefor, of motors foroperating the regulators, and a transformer the primary winding of whichis connected between corresponding terminals of the translating devicesand the secondary of which is connected to the regulator-operatingmotors by means of its end terminals and an intermediate connection.

2. The combination with a plurality of translating devices andvoltage-regulators therefor, of motors for operating the regulators anda transformer for governing the speeds of the motors and therebyequalizing the voltages supplied by the regulators to the translatingdevices.

3. The combination with a supply-circuit, a plurality of main electricmotors and a plurality of motor-operated voltage-regulators for varyingthe speed of said main motors, of an adjListing-transformer theprimarywinding of which is connected between corresponding points in thecircuits of the main motors and the secondary winding of which has itsend terminals respectively connected to the terminals of theregulator-operating motors and an intermediate point connected to thesupply-circuit.

4:. The combination with a supply-circuit, a plurality of main electricmotors and a plurality of motor-operated voltage-regulators for varyingthe speed of said main motors, of an adjListing-transformer the primarywinding of which is connected between corresponding points in thecircuits of the main motors and the end terminals of the secondarywinding of which are connected to terminals of non-correspondingregulator-operating motors and an intermediate point of which isconnected to the supply-circuit.

In testimony whereof I have hereunto subscribed my name this 31st day ofMarch, 1905.

FRANK CONRAD.

Witnesses:

S. E. J OHANNESEN, BIRNEY HINES.

